First, make sure the Mac still thinks it is enrolled. Open Terminal and run the following command: “profiles status -type enrollment”. You should see a response “MDM enrollment: Yes”.
Check the time on the Mac. If the time is too far off, it can cause SSL errors which could prevent it from communicating.
Cycle the network connection on the Mac, either via a reboot or by manually disconnecting/reconnecting. After cycling, open the Safari and make sure it is working.
Send an inventory command from KACE Cloud. If able, the Mac should check-in. Also, try sending a Lock command to the device. If the device receives the command, then it should also be able to check-in.
Check any local machine firewall settings to make sure there’s nothing blocking the outbound communications.
If the Mac is a VM, make sure the serial number is not shared with another VM or physically enrolled Mac.
Finally, if none of these work, check the device history in KACE Cloud to see if there is anything unusual in there [Devices | (select device) | General |Device History].